CN1498438A - Non-aqueous electrolyte and lithium secondary battery - Google Patents

Abstract

The present invention relates to the use of a non-aqueous electrolytic solution prepared by adding 0.1 to 10% by weight of tertiary alkylbenzene, preferably in combination with 0.1 to 1.5% by weight of a biphenyl compound, to a solution in which an electrolyte is dissolved in a non-aqueous solvent. Lithium secondary batteries excellent in charging safety and battery characteristics such as cycle characteristics, electric capacity, and storage characteristics are effective.

Description

Non-aqueous electrolyte and lithium secondary battery

technical field

The present invention relates to a lithium secondary battery excellent in safety such as preventing battery overcharge, and battery characteristics such as cycle characteristics, capacity, and storage characteristics, and also relates to a nonaqueous electrolyte solution useful in the manufacture of lithium secondary batteries.

Background technique

In recent years, lithium secondary batteries have been widely used as power sources for driving small electronic devices and the like. In addition, not only portable electronic/communication devices such as compact cameras, mobile phones, and notebook computers, but also power supplies for automobiles are also expected. The lithium secondary battery is composed of a positive electrode, a non-aqueous electrolytic solution, and a negative electrode. In particular, a lithium secondary battery using a lithium composite oxide such as _LiCoO as a positive electrode and a carbon material or lithium metal as a negative electrode is preferably used. In addition, it is preferable to use carbonates such as ethylene carbonate (EC) and propylene carbonate (PC) as the non-aqueous solvent of the electrolytic solution for lithium secondary batteries.

In such a lithium secondary battery, during overcharging to increase the normal operating voltage, excess lithium is released from the positive electrode and simultaneously deposited on the negative electrode, resulting in the formation of dendrites. Therefore, the positive and negative electrodes are chemically destabilized. When the positive and negative electrodes become chemically unstable, they react with carbonates in the non-aqueous electrolytic solution for a short time and decompose, resulting in a rapid exothermic reaction. Therefore, the battery generates heat abnormally, and there arises a problem that the safety of the battery is impaired. In such a case, the problem increases as the current energy density generated from the lithium secondary battery increases.

So far, it has been proposed that safety against overcharging can be ensured by adding a small amount of aromatic compounds as additives to the electrolytic solution.

JP-A-7-302614 describes a technique of using a π-electron orbital having a molecular weight of 500 or less and having a reversible redox potential at a potential higher (expensive) than the positive electrode potential at full charge. Organic compounds, such as compounds represented by anisole derivatives, are used as electrolyte additives.

In Japanese Patent Laid-Open No. 2000-156243, a technique is also described to use an organic compound having a reversible redox potential at a potential higher (expensive) than the positive electrode potential at full charge, such as Compounds represented by anisole derivatives, biphenyl, 4,4'-dimethylbiphenyl, etc. are used as additive components of the electrolytic solution.

The aforementioned organic compounds such as anisole derivatives and biphenyl derivatives can ensure the safety of the battery during overcharging by causing shuttling in the battery.

A method has been proposed in JP-A-9-106835 (corresponding to US-5879834), that is, a carbon material is used for the negative electrode, and as an additive to the electrolyte, biphenyl, 3-R-thiophene, 3-chlorothiophene, furan, etc., use the phenomenon of polymerization of biphenyl and the like at a voltage exceeding the maximum operating voltage of the battery to increase the internal resistance of the battery to ensure the safety of the battery during overcharging Methods.

In JP-A-9-171840 (corresponding to US-5776627 and US-6033797), a method has been proposed, that is, similarly, using biphenyl, 3-R-thiophene, 3-chlorothiophene, furan, etc., Using the phenomenon of polymerization of biphenyl and the like at a voltage exceeding the maximum operating voltage of the battery to generate gas and operate the internal power-off device to cause an internal short circuit to ensure the safety of the battery when it is fully charged.

A method was proposed in JP-10-321258, that is, similarly, using biphenyl, 3-R-thiophene, 3-chlorothiophene, furan, etc., using biphenyl, etc., at a voltage exceeding the maximum operating voltage of the battery The phenomenon of polymerization, through the generation of conductive polymers, causes an internal short circuit to ensure the safety of the battery when it is fully charged.

The scheme proposed in the Japanese Patent Application Laid-Open No. 10-275632 is to add a nonionic aromatic compound with an alkyl group in an organic electrolyte solution using a chain ester as a main solvent in a secondary battery as the nonionic aromatic compound with an alkyl group. Specific examples of ionic aromatic compounds include trimellitate, tris-2-ethylhexyl trimellitate, dimethyl phthalate, dibutyl phthalate, butylbenzene ( normal, tertiary or iso), cyclohexylbenzene, toluene, etc.

Japanese Patent Laid-Open Publication No. 11-162512 (corresponding to US-6074777) pointed out the following problems, that is, in a battery to which biphenyl or the like is added, the cycle is repeated at a voltage upper limit exceeding 4.1 V, and the battery is exposed to In a state of charge and discharge at a high temperature of 40° C. or higher, battery characteristics such as cycle characteristics tend to deteriorate, and this tendency becomes more remarkable as the amount of addition increases. Therefore propose a kind of electrolyte solution that adds 2,2-diphenylpropane or its similar compound, utilize the phenomenon that 2,2-diphenylpropane or its similar compound carry out polymerization under the voltage exceeding the maximum working voltage of battery, occur Gas, and by making the internal power-off device work, or the conductive polymer, so that the internal short circuit occurs, to ensure the safety of the battery when fully charged.

The anisole derivatives or biphenyl derivatives proposed in JP-A-7-302614 or JP-A-2000-156243 can effectively function for overcharging due to redox shuttling, however, the cycle characteristics and preservation In terms of characteristics, there is a problem of adverse effects. That is, when the anisole derivative or biphenyl derivative of the proposed scheme is used at a high temperature above 40°C or at a normal operating voltage, when a slightly higher voltage is locally obtained, the anisole derivative will be charged and discharged simultaneously. Or biphenyl derivatives are gradually decomposed, and there is still the problem of deterioration of battery characteristics in the past. Therefore, there is a problem that the anisole derivative or the biphenyl derivative is gradually decomposed together with normal charging and discharging, and thus safety cannot be sufficiently ensured even after 300 cycles.

In addition, it is the same as biphenyl, 3-R-thiophene, 3-chlorothiophene, and furan proposed in JP-A-9-106835, JP-9-171840, and JP-10-321258. Charging works effectively, and as pointed out in the above-mentioned Japanese Patent Laid-Open No. 11-162512, there is a problem that there is a bad influence on cycle characteristics and retention characteristics, and with the increase in the amount of biphenyl added, these The problem becomes more pronounced. That is, since biphenyl and the like are oxidatively decomposed at a potential of 4.5 V or less, when used at a high temperature above 40°C or at a normal operating voltage, when the local voltage becomes slightly higher, the decomposition of biphenyl and the like is less , so the cycle life decreases. In addition, there is a problem that the biphenyl is not decomposed gradually along with charge and discharge, so even after 300 cycles, there is a problem that the safety cannot be sufficiently ensured.

In addition, although the battery with the addition of 2,2-diphenylpropane and its similar compounds proposed in the Japanese Patent Laid-Open No. 11-162512 is not as good as the safety of the battery with biphenyl for overcharging, it is better than anything else. Batteries that are not charged are more secure against overcharging. In addition, it is well known that the cycle characteristics of batteries added with 2,2-diphenylpropane are better than those of batteries added with biphenyl, but the cycle characteristics are worse than those of batteries without any addition. Therefore, it is also known that it is necessary to sacrifice a part of safety in order to obtain better cycle characteristics than biphenyl-added batteries.

The object of the present invention is to provide a lithium secondary battery excellent in safety such as prevention of overcharge of the battery, and battery characteristics such as cycle characteristics, electric capacity, and storage characteristics, and to provide a lithium secondary battery with such high safety and cycle characteristics. Excellent non-aqueous electrolyte solution for the manufacture of lithium secondary batteries.

Contents of the invention

The invention relates to an electrolytic solution, which is a non-aqueous electrolytic solution for a lithium secondary battery in which an electrolyte is dissolved in a non-aqueous solvent, and is characterized in that the non-aqueous electrolytic solution also contains 0.1% to 10% by weight of Tertiary alkylbenzene compound and 0.1% by weight to 1.5% by weight of biphenyl compound.

The above-mentioned tertiary alkylbenzene compound added in the non-aqueous electrolytic solution of the present invention is preferably (R ¹ )(R ² )(R ³ )C-φ ¹ [wherein, R ¹ , R ² , and R ³ each independently represent an alkyl group with 1 to 4 carbon atoms, ^{and φ1} represents a benzene ring that may have 1 to 5 substituents on the ring], particularly preferably, the benzene ring has no substituents compound of. Particularly preferred tert-alkylbenzene compounds are tert-butylbenzene and tert-amylbenzene. In addition, as the tertiary alkylbenzene compound, a compound having 1 to 5 hydrocarbon groups and/or halogen atoms as substituents on the benzene ring is also preferable.

The above-mentioned biphenyl compound added in the non-aqueous electrolytic solution of the present invention is preferably φ ² -φ ³ [φ ² and φ ³ , each independently of each other, and means that there may be 1 to 5 substituents on the ring The compound represented by the benzene ring]. As this preferable biphenyl compound, biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 4-methylbiphenyl, 4-ethylbiphenyl, and 4-tert-butyl biphenyl. The biphenyl compound used in the present invention preferably has an oxidation potential of 4.5 V or less.

In addition, the present invention is also an electrolytic solution, which is a non-aqueous electrolytic solution for a lithium secondary battery in which an electrolyte is dissolved in a non-aqueous solvent, and is characterized in that the non-aqueous electrolytic solution also contains 0.1 wt % to 20 wt % of tertiary alkylbenzene compounds (however, the number of carbon atoms in the tertiary alkyl group is within the range of 5 to 13). As a representative example of the t-alkylbenzene compound, t-amylbenzene is mentioned. That is, tertiary alkylbenzene compounds such as tert-amylbenzene having a tertiary alkyl group having 5 to 13 carbon atoms are advantageous in accomplishing the object of the present invention even if they are not used in combination with biphenyl compounds. effect.

In addition, the present invention also relates to a lithium secondary battery composed of a positive pole, a negative pole, and the above-mentioned non-aqueous electrolytic solution of the present invention, wherein said positive pole is made of a composite oxide containing cobalt, nickel or manganese and lithium , and said negative electrode is made of lithium metal, lithium alloy, or materials capable of absorbing and releasing lithium.

As mentioned above, conventionally known mechanisms for preventing overcharge include redox shuttling at a potential near 4.5 V, a method of increasing the internal resistance of the battery by polymerization of additives at a potential below 4.5 V, and a method of increasing the internal resistance of the battery by A method of generating an internal short circuit by operating an internal cutoff device with generated gas, a method of ensuring battery safety against overcharge by generating an internal short circuit by generating a conductive polymer, and the like.

On the other hand, the overcharge prevention mechanism of the non-aqueous electrolytic solution using tertiary alkylbenzene compound as the additive of the present invention can be considered to be that the tertiary alkylbenzene compound contained in the nonaqueous electrolytic solution has a positive effect on lithium at +4.6V～+ Oxidative decomposition is carried out at a potential of 5.0V, so the dissolution of cobalt or nickel in the positive electrode is promoted during overcharge. Since the cobalt or nickel is precipitated on the negative electrode, the lithium metal precipitated on the negative electrode and the carbonate in the non-aqueous electrolyte The response is suppressed before it occurs.

In addition, in the present invention, it is considered that an internal short circuit is caused by depositing cobalt or nickel on the negative electrode inside the battery depending on the case, thereby achieving an effect of preventing overcharge. As a result, it can be inferred that the safety of the battery can be sufficiently ensured.

Furthermore, in the present invention, by adding a small amount of biphenyl compound of 0.1% to 1.5% by weight to the tertiary alkylbenzene compound, it helps to improve the overcharge prevention effect of the tertiary alkylbenzene compound. Unpredictable effects have been achieved on the known low battery characteristics.

In addition, the tertiary alkylbenzene compound contained in the non-aqueous electrolyte has an oxidation potential of +4.6V to +5.0V for lithium, so even if the charge and discharge are repeated at a high temperature above 40°C or at a normal operating voltage, the voltage is partially More than 4.2V tert-alkylbenzene compound does not decompose.

In addition, when only a small amount of biphenyl compound is added at 0.1% to 1.5% by weight, although no overcharge prevention effect is found, since the decomposition of the biphenyl compound is extremely small, it can be reversed by using it in combination with a tertiary alkylbenzene compound. See improvements in battery characteristics. Furthermore, when the overcharge test was performed after 300 cycles, safety could be sufficiently ensured due to the overcharge preventing effect of the above-mentioned tertiary alkylbenzene compound. It can be understood that, because of this, it is possible to provide a lithium secondary battery that not only has excellent safety such as prevention of overcharge of the battery, but also has excellent battery characteristics such as cycle characteristics, electric capacity, and storage characteristics.

Best way to implement the invention

Examples of the tert-alkylbenzene compound contained in the electrolytic solution in which the electrolyte is dissolved in the non-aqueous solvent include the following compounds.

tert-butylbenzene, 1-fluoro-4-tert-butylbenzene, 1-chloro-4-tert-butylbenzene, 1-bromo-4-tert-butylbenzene, 1-iodo-4-tert-butylbenzene, 5 -tert-butyl-m-xylene, 4-tert-butyltoluene, 3,5-di-tert-butyltoluene, 1,3-di-tert-butylbenzene, 1,4-di-tert-butylbenzene, 1,3,5-tri-tert-butylbenzene, tert-amylbenzene, (1-ethyl-1-methylpropyl)benzene, (1,1-diethylpropyl)benzene, (1-ethyl Base-1-methylbutyl)benzene, (1-ethyl-1-ethylbutyl)benzene, (1,1,2-trimethylpropyl)benzene, 1-fluoro-4-tert-amyl Benzene, 1-chloro-4-tert-amylbenzene, 1-bromo-4-tert-amylbenzene, 1-iodo-4-tert-amylbenzene, 5-tert-amyl-m-xylene, 1-methyl-4 - tert-amylbenzene, 3,5-di-tert-amyltoluene, 1,3-di-tert-amylbenzene, 1,4-di-tert-butylbenzene, and 1,3,5-tri-tert-amylbenzene Benzene.

The tertiary alkylbenzene compounds can be used alone or in combination of two or more.

Among the tert-alkylbenzene compounds added to the non-aqueous electrolytic solution of the present invention, tert-butylbenzene and those having a substituent such as an alkyl group or a halogen atom on its ring are preferable. It can also be mentioned that (R ¹ )(R ² )(R ³ )C-φ ¹ [wherein, R ¹ is an alkyl group with 2 to 4 carbon atoms, and R ² and R ³ independently represent is an alkyl group having 1 to 4 carbon atoms, and ^φ1 represents a compound represented by a benzene ring which may have 1 to 5 substituents on the ring]. The use of the latter compound can especially improve the cycle characteristics of the non-aqueous electrolytic solution.

In the above compound represented by (R ¹ )(R ² )(R ³ )C-φ ¹ , R ¹ is preferably an alkyl group such as ethyl, propyl, or butyl, and R ² and R ³ are preferably Yes, each independently represents an alkyl group such as a methyl group, an ethyl group, a propyl group, or a butyl group. The alkyl group at this time may be a straight-chain alkyl group or a branched-chain alkyl group.

In addition, on the benzene ring represented by ^φ1 , there may be 1 to 5 substituents on the ring, and the substituents preferably have, independently, straight chains such as methyl, ethyl, propyl, and butyl. Alkyl, and branched alkyl such as isopropyl, isobutyl, sec-butyl, tert-butyl, tert-amyl. In addition, a cycloalkyl group having 3 to 6 carbon atoms such as cyclopropyl group and cyclohexyl group may also be used. In addition to the phenyl and benzyl groups, alkyl-substituted phenyl and benzyl groups such as tolyl, tert-butylphenyl, tert-butylbenzyl, and tert-amylphenyl may be used. Also preferred are halogen atoms such as fluorine atom, chlorine atom, bromine atom, or iodine atom. Those having such a hydrocarbon group having 1 to 12 carbon atoms or a halogen atom are preferred.

Specific examples of the above-mentioned tert-alkylbenzene compound include tert-amylbenzene, (1-ethyl-1-methylpropyl)benzene, (1,1-diethylpropyl)benzene, (1 , 1-dimethylbutyl)benzene, (1-ethyl-1-methylbutyl)benzene, (1-ethyl-1-ethylbutyl)benzene, (1,1,2-trimethyl Propyl) benzene, etc. In addition, examples of tert-amylbenzene derivatives include 1-methyl-4-tert-amylbenzene, 5-tert-amyl-m-xylene, 1,3-di-tert-amylbenzene, 1,4-di-tert-amylbenzene, 1,3,5-tri-tert-amylbenzene, 4-bromo-tert-amylbenzene, 4-fluoro-tert-amylbenzene, 4-chloro-tert-amylbenzene , 4-iodo-tert-amylbenzene, etc.

Examples of biphenyl compounds include biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 4-methylbiphenyl, 4-ethylbiphenyl, and 4-tert-butylbiphenyl, etc. In particular, a part of the above-mentioned tert-butylbenzene and the like whose oxidation potential is as high as 4.8 to 5.0 V is replaced by a biphenyl compound (for example, o-terphenyl) whose oxidation potential is as low as 4.5 V, thereby improving the effect of preventing overcharge.

Furthermore, when a part of the tertiary alkylbenzene compound is replaced by biphenyl, the content of the tertiary alkylbenzene compound is preferably less than 10 times the weight of the biphenyl compound, more preferably 0.3 to 5 times the amount, particularly preferably 0.5 to 3 times the weight of the biphenyl compound. Double the amount.

As described above, by using in combination a tertiary alkylbenzene compound and a biphenyl compound having different oxidation potentials, it is possible to enhance the overcharge prevention effect and improve battery characteristics.

When the content of the tert-alkylbenzene compound is too large, the conductivity of the electrolytic solution changes and the performance of the battery decreases, and when it is too small, a sufficient overcharge prevention effect cannot be obtained, so it is 0.1% by weight to 10% by weight relative to the weight of the electrolytic solution , particularly preferably 1 to 5% by weight.

In addition, when the content of the biphenyl compound is too large, the biphenyl compound will be decomposed in the battery during normal use, and the battery performance will be reduced. If it is too small, sufficient overcharge (prevention) effect and battery performance will not be obtained. The weight of the liquid is 0.1% by weight to 1.5% by weight, particularly preferably 0.3% by weight to 0.9% by weight.

As the nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC ) and other cyclic carbonates, γ-butyrolactone and other lactones, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC) and other chain carbonates, Tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, etc. Ethers, nitriles such as acetonitrile, esters such as methyl propionate, methyl trimethylacetate, and octyl trimethylacetate, amides such as dimethylformamide.

These nonaqueous solvents may be used alone or in combination of two or more. The combination of nonaqueous solvents is not particularly limited, for example, can enumerate, the combination of cyclic carbonates and chain carbonates, the combination of cyclic carbonates and lactones, the combination of cyclic carbonates and tris Various combinations such as combinations of species and chain carbonates.

In order to produce a solute dissolved in a non-aqueous solvent for a non-aqueous electrolyte, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiC( SO ₂ CF ₃ ) ₃ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso- C ₃ F ₇ ) etc. These electrolytes may be used alone or in combination of two or more. These electrolytes are usually dissolved in the above non-aqueous solvent at a concentration of 0.1 to 3M, preferably 0.5 to 1.5M.

The electrolytic solution of the present invention is obtained by mixing the above-mentioned non-aqueous solvent, dissolving the above-mentioned electrolyte therein, and then dissolving at least one of the above-mentioned tertiary alkylbenzene compounds and, if necessary, at least one of the biphenyl compounds. . The electrolytic solution of the present invention is preferably used as a constituent material of a secondary battery, particularly preferably used as a constituent material of a lithium secondary battery. There are no particular limitations on the constituent members other than the electrolytic solution constituting the secondary battery, and various constituent members conventionally used can be used.

For example, as the positive electrode active material, a composite metal oxide containing cobalt or nickel and lithium is preferably used. Examples of such composite metal oxides include LiCoO ₂ , LiNiO ₂ , LiCo _1-x Ni _x O ₂ (0.01<x<1), and LiMn ₂ O ₄ . In addition, LiCoO ₂ and LiMn ₂ O ₄ , LiCoO ₂ and LiNiO ₂ , and LiMn ₂ O ₄ and LiNiO ₂ may be used in a proper mixture.

The positive electrode is made by combining the above-mentioned positive electrode active material with conductive agents such as acetylene black and carbon black, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene and butadiene copolymer (SBR), acrylonitrile and Butadiene copolymer (NBR), carboxymethyl cellulose (CMC) and other binders are kneaded to make a positive electrode mixture, and the positive electrode material is placed on an aluminum or stainless steel foil or strip plate as a collector It is made by calendering and heat treatment under vacuum at a temperature of about 50-250°C for about 2 hours.

As the negative electrode (negative electrode active material), you can use lithium metal or lithium alloy, or carbon materials that can absorb and release lithium [pyrolytic carbon, coke, graphite (artificial graphite, natural graphite, etc.), organic polymer compound combustion Body, carbon fiber], or composite tin oxide and other substances. It is particularly preferable to use a carbon material having a graphite-type crystal structure with a crystal plane (002) whose interplanar distance (d ₀₀₂ ) is 0.335 to 0.340 nm (nanometer). In addition, if the carbon material is a powder material, it can be mixed with ethylene-propylene-diene terpolymer (EPDM), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene and butadiene copolymer (SBR ), acrylonitrile and butadiene copolymer (NBR), carboxymethyl cellulose (CMC) and other binders are mixed to make negative electrode mixture.

The structure of the lithium secondary battery of the present invention is not particularly limited, and as an example, a coin-type battery or a polymer battery having a single-layer or multi-layer positive electrode, a negative electrode, and a separator can also be mentioned, and a cylindrical battery Cylindrical batteries, square batteries, etc. with positive electrodes, negative electrodes, and cylindrical separators. In addition, known polyolefin microporous films, woven fabrics, nonwoven fabrics, and the like can be used as the separator.

In the lithium secondary battery of the present invention, even when the maximum operating voltage is greater than 4.2V, it still has excellent cycle characteristics for a long time, especially when the maximum operating voltage is greater than 4.3V, it also has excellent cycle characteristics. . The cut-off voltage can reach more than 2.0V, and further can reach more than 2.5V. There is no particular limitation on the current value, but it is usually available at . It is used under a constant current discharge of 0.1 to 3C. In addition, the lithium secondary battery in the present invention can be charged and discharged in a wide range of -40 to 100°C, but preferably 0 to 80°C.

Example 1

[Preparation of Electrolyte]

Prepare a non-aqueous solvent of EC/PC/DEC (capacity ratio) = 30/5/65, dissolve LiPF ₆ in it to a concentration of 1M after preparing an electrolyte, and then make it 2.5% by weight and 0.9% by weight relative to the electrolyte The tertiary alkylbenzene compound and the biphenyl compound are added slowly.

[Production of Lithium Secondary Battery and Measurement of Battery Characteristics]

90% by weight of LiCoO ₂ (positive electrode active material), 5% by weight of acetylene black (conductive agent), and 5% by weight of polyvinylidene fluoride (binder) were mixed, and 1-methyl-2-pyrrolidone was added thereto. Make a slurry and apply to aluminum foil. Then, this coating was dried, and press-molded to prepare a positive electrode. Mix 95% by weight of artificial graphite (negative electrode active material) and 5% by weight of polyvinylidene fluoride (binder), add 1-methyl-2-pyrrolidone to it to form a slurry and coat it on copper foil . Then, it was dried and press-molded to prepare a negative electrode.

Then, the electrolytic solution was poured into a cylindrical container using a polypropylene microporous membrane separator to fabricate a 18650-size cylindrical battery (diameter: 18 mm, height: 65 mm). For this cell, a pressure vent and an internal galvanic break are provided.

Using this 18650 battery, in order to conduct a cycle test, it was charged at a constant current of 1.45A (1C) at a high temperature (45°C) to 4.2V, and then charged at a constant voltage at a cut-off voltage of 4.2V for a total of 3 hours. Then, under a constant current of 1.45A (1C), charge and discharge are repeated until the cut-off voltage is 2.5V. The initial discharge capacity is equivalent to the case of using 1M LiPF ₆ +EC/PC/DEC (capacity ratio)=30/5/65 as the electrolytic solution. When the battery characteristics were measured after 300 cycles, the discharge maintenance rate when the initial discharge capacity reached 100% was 84.4%. In addition, the high temperature retention property is also good. Furthermore, an overcharge test was performed by continuously charging at a constant current of 2.9 A (2 C) from a fully charged state at normal temperature (20° C.) using a 18650 battery subjected to a cycle test repeated 300 times. At this time, the current interruption time was 22 minutes, and the highest surface temperature of the battery after the current interruption was 67°C. Table 1 shows the material conditions and battery characteristics of the 18650-sized cylindrical battery.

Example 2

A cylindrical battery was fabricated in the same manner as in Example 1, except that the amount of biphenyl used was 0.5% by weight relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Example 3

A cylindrical battery was produced in the same manner as in Example 1, except that the amount of biphenyl used was 1.3% by weight relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Example 4

A cylindrical battery was produced in the same manner as in Example 1, except that 0.9% by weight o-terphenyl was used instead of biphenyl relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Example 5

Except that 2.5% by weight of tert-amylbenzene was used instead of tert-butylbenzene relative to the electrolyte, and 0.9% by weight of 4-ethylbiphenyl was used instead of biphenyl relative to the electrolyte, the rest was the same as in Example 1. Operation to make a cylindrical battery. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Example 6

In addition to using tert-butylbenzene and pentylbenzene as tert-alkylbenzene at 2% by weight relative to the electrolyte, and using 0.5% by weight of 4-methylbiphenyl instead of biphenyl relative to the electrolyte, the rest are the same as A cylindrical battery was produced in the same manner as in Example 1. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative example 1

A cylindrical battery was produced in the same manner as in Example 1, except that no tertiary alkylbenzene compound and biphenyl compound were added. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative example 2

A cylindrical battery was fabricated in the same manner as in Example 1, except that the amount of biphenyl used was 1.3% by weight relative to the electrolyte solution and no tertiary alkylbenzene compound was used. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative example 3

A cylindrical battery was produced in the same manner as in Comparative Example 1, except that the amount of biphenyl used was 4% by weight relative to the electrolyte solution and no tertiary alkylbenzene compound was used. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Example 7

A cylindrical battery was produced in the same manner as in Example 5, except that LiNI _0.8 Co _0.2 O ₂ was used instead of LiCoO ₂ as the positive electrode active material. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative example 4

Except that no tertiary alkylbenzene compound and biphenyl compound were added, the cylindrical battery was produced in the same manner as in Example 7, and the battery characteristics were measured. The material conditions and battery characteristics of the battery are shown in Table 1.

Example 8

A cylindrical battery was produced in the same manner as in Example 1, except that 3.0% by weight of 4-fluoro-tert-amylbenzene was used instead of tert-butylbenzene relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative Example 5

A cylindrical battery was fabricated in the same manner as in Comparative Example 1 except that 3.0% by weight of toluene was used relative to the electrolyte solution and 0.5% by weight of biphenyl was used relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative example 6

A cylindrical battery was fabricated in the same manner as in Comparative Example 1 except that 3.0% by weight of n-butylbenzene was used with respect to the electrolytic solution and 0.5% by weight of biphenyl was used with respect to the electrolytic solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative Example 7

A cylindrical battery was produced in the same manner as in Comparative Example 1 except that 3.0% by weight of di-n-butylbenzene and 0.5% by weight of biphenyl were used relative to the electrolyte solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Comparative Example 8

A cylindrical battery was fabricated in the same manner as in Comparative Example 1, except that 3.0% by weight of 4-fluorotoluene was used with respect to the electrolytic solution and 0.5% by weight of biphenyl was used with respect to the electrolytic solution. Table 1 shows the material conditions of the battery, the discharge capacity retention rate after 300 cycles, the current interruption time, and the maximum surface temperature of the battery after the current interruption.

Table 1 positive electrode negative electrode Content of tert-alkylbenzene derivatives + biphenyl derivatives (wt%) Electrolyte composition capacity ratio Current interruption time (minutes) The maximum temperature of the battery (℃) 300 cycles discharge capacity maintenance rate% Example 1 _LiCoO2 artificial graphite tert-butylbenzene (2.5) + biphenyl (0.9) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty two 67 84.4 Example 2 _LiCoO2 artificial graphite tert-butylbenzene (2.5) + biphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty four 69 84.0 Example 3 _LiCoO2 artificial graphite tert-butylbenzene (2.5) + biphenyl (1.3) 1M LiPF ₆ EC/PC/DEC＝30/5/65 20 66 82.7 Example 4 _LiCoO2 artificial graphite tert-butylbenzene(2.5)+o-Terlfenil(0.9) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty two 67 84.3 Example 5 _LiCoO2 artificial graphite tert-amylbenzene (2.5) + 4 ethyl biphenyl (0.9) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty one 66 82.3 Example 6 _LiCoO2 artificial graphite tert-butylbenzene (2) tert-amylbenzene (2) + 4-methylbiphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty one 66 85.1 Comparative example 1 _LiCoO2 artificial graphite none 1M LiPF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 82.8 Comparative example 2 _LiCoO2 artificial graphite Biphenyl (1.3) 1M LiPF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 78.3 Comparative example 3 _LiCoO2 artificial graphite Biphenyl (4) 1M LiPF ₆ EC/PC/DEC＝30/5/65 18 83 72.1 Example 7 LiNi _0.8 Co _0.2 O ₂ artificial graphite tert-amylbenzene (2.5)+4-ethylbiphenyl ((0.9) 1M LiPf ₆ EC/PC/DEC＝30/5/65 twenty one 67 82.5 Comparative example 4 LiN _0.8 Co _0.2 O ₂ artificial graphite none 1M LiPF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 80.4 Example 8 _LiCoO2 artificial graphite 4-fluoro-tert-amylbenzene (3) + biphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 twenty three 68 84.3 Comparative Example 5 _LiCoO2 artificial graphite Toluene (3) + biphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 81.2 Comparative Example 6 _LiCoO2 artificial graphite n-butylbenzene (3) + biphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 80.1 Comparative Example 7 LiCoO2 artificial graphite Di-n-butylphthalate (3) + biphenyl (0.5) 1M LipF ₆ EC/PC/DEC＝30/5/65 31 thermal runaway 78.4 Comparative example 8 LiCoO2 artificial graphite 4-fluorotoluene (3) + biphenyl (0.5) 1M LiPF ₆ EC/PC/DEC＝30/5/65 25 thermal runaway 79.8

It can be seen from the above Examples 1 to 8 that cobalt and nickel were sufficiently deposited on the negative electrode during overcharge. According to the present invention, the lithium secondary battery using the non-aqueous electrolytic solution added with the tertiary alkylbenzene compound and the biphenyl compound is superior to the secondary battery of the comparative example in terms of overcharge safety and cycle characteristics.

Example 11

[Preparation of non-aqueous electrolyte]

Prepare a non-aqueous solvent of EC:PC:DEC (capacity ratio) = 30:5:65, dissolve LiPF ₆ in it to a concentration of 1M, prepare an electrolyte, and then add 2.0% by weight to the non-aqueous electrolyte tert-amylbenzene.

[Production of Lithium Secondary Battery and Measurement of Battery Characteristics]

80% by weight of LiCoO ₂ (positive electrode active material), 10% by weight of acetylene black (conductive agent), and 10% by weight of polyvinylidene fluoride (binder) were mixed, and 1-methyl-2- The product of the pyrrolidone solvent is coated on an aluminum foil, dried, press-molded, and heat-treated to prepare a positive electrode. 90% by weight of artificial graphite (negative electrode active material) and 10% by weight of polyvinylidene fluoride (binder) are mixed, 1-methyl-2-pyrrolidone solvent is added thereto, and the mixed product is coated on On the copper foil, it is dried, press-formed, and heat-treated to prepare the negative electrode. Then, using a polypropylene microporous membrane separator, the above-mentioned non-aqueous electrolytic solution was injected to fabricate a coin battery (diameter 20 mm, thickness 3.2 mm).

Using this coin cell, at room temperature (20°C), charge at a constant current and constant voltage of 0.8mA for 5 hours to a cut-off voltage of 4.2V, then discharge at a constant current of 0.8mA to a cut-off voltage of 2.7V, and repeat this process. Charge and discharge. The initial discharge capacity was almost equivalent to the case of using 1M LiPF ₆ -EC/PC/DEC (capacity ratio) = 30/5/65 as the non-aqueous electrolytic solution without adding tert-alkylbenzene derivatives. When the battery characteristics were measured after 50 cycles, the discharge capacity retention rate when the initial discharge capacity reached 100% was 92.8%. In addition, low-temperature characteristics are also good. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 12

Except that tert-amylbenzene of 5.0% by weight relative to the non-aqueous electrolyte is used as an additive, the non-aqueous electrolyte is prepared in the same manner as in Example 11 to make a coin battery, and when measuring the battery characteristics after 50 cycles, the discharge capacity The maintenance rate was 91.5%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 13

Except that tert-amylbenzene of 0.5% by weight relative to the nonaqueous electrolyte is used as an additive, the nonaqueous electrolyte is prepared in the same manner as in Example 11 to make a coin battery, and when measuring the battery characteristics after 50 cycles, the discharge capacity The maintenance rate was 90.3%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Comparative Example 11

A non-aqueous solvent of EC:PC:DEC (capacity ratio)=30:5:65 was prepared, and LiPF ₆ was dissolved therein to a concentration of 1M. At this time, no tert-alkylbenzene derivatives were added at all. Using this non-aqueous electrolytic solution, a coin battery was fabricated in the same manner as in Example 11, and battery characteristics were measured. Regarding the initial discharge capacity, the discharge capacity maintenance rate after 50 cycles was 82.6%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 14

Prepare a non-aqueous solvent of EC:PC:DEC (capacity ratio) = 30:5:65, dissolve LiPF ₆ in it to a concentration of 1M, prepare an electrolyte, and then add 2.0% by weight to the non-aqueous electrolyte 4-tert-amyltoluene.. Using this non-aqueous electrolytic solution, a coin cell was produced in the same manner as in Example 11, and when the battery characteristics were measured, the initial discharge capacity was compared with LiPF ₆ -EC/PC/DEC (capacity ratio 30/5/65) is almost the same as the non-aqueous electrolyte (Comparative Example 11). When measuring the battery characteristics after 50 cycles, the discharge capacity retention rate when the initial discharge capacity reaches 100% is 92.1 %. In addition, low-temperature characteristics are also good. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 15

Except that 2.0% by weight of (1,1-diethylpropyl) benzene is used as an additive relative to the non-aqueous electrolyte, the non-aqueous electrolyte is prepared in the same manner as in Example 11 to make a coin battery, and 50 cycles are measured. According to the final battery characteristics, the discharge capacity retention rate was 91.9%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 16

Except using EC/PC/DEC/DMC (capacity ratio 30/5/30/35) as non-aqueous solvent, using natural graphite instead of artificial graphite as negative electrode active material, all the other operate and prepare non-aqueous electrolyte in the same way as in Example 11 When a coin battery was produced and the battery characteristics were measured after 50 cycles, the discharge capacity retention rate was 92.8%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 17

In addition to using 1M LiPF ₆ -EC/PC/MEC/DMC (capacity ratio 30/5/50/15) as the non-aqueous electrolyte, and using LiNi _0.8 Co _0.2 O ₂ instead of LiCoO ₂ as the positive electrode active material, the rest and implementation In Example 11, the non-aqueous electrolyte solution was prepared in the same manner to produce a coin battery, and when the battery characteristics were measured after 50 cycles, the discharge capacity retention rate was 91.1%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 18

In addition to using 1M LiPF ₆ -EC/PC/DEC/DMC (capacity ratio 30/5/30/35) as the non-aqueous electrolyte, and using LiNI _0.8 Co _0.2 O ₂ instead of LiCoO ₂ as the positive electrode active material, the rest and implementation In Example 11, the non-aqueous electrolyte solution was prepared in the same manner to produce a coin battery, and when the battery characteristics were measured after 50 cycles, the discharge capacity retention rate was 92.6%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Example 19

Except for using 3.0% by weight of 4-fluoro-tert-amylbenzene with respect to the non-aqueous electrolytic solution as an additive, the non-aqueous electrolytic solution was prepared in the same manner as in Example 11 to prepare a coin battery, and the battery characteristics after 50 cycles were measured. , The discharge capacity maintenance rate was 92.7%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Comparative Example 12

Except using the toluene that is 3.0% by weight relative to the non-aqueous electrolytic solution, all the other operations were performed in the same manner as Comparative Example 11 to prepare the non-aqueous electrolytic solution to make a coin battery, and when measuring the battery characteristics after 50 cycles, the discharge capacity retention rate was 81.3 %. Table 2 shows the production conditions and battery characteristics of the coin cell.

Comparative Example 13

Except that the n-butylbenzene that is 3.0% by weight relative to the non-aqueous electrolytic solution is used as an additive, the non-aqueous electrolytic solution is prepared in the same manner as in Comparative Example 11 to make a coin battery, and when the battery characteristics after 50 cycles are measured, the discharge capacity The maintenance rate was 79.7%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Comparative Example 14

Except that the di-n-butyl phthalate that is 3.0% by weight relative to the non-aqueous electrolyte is used as an additive, the non-aqueous electrolyte is prepared in the same manner as in Comparative Example 11 to make a coin battery, and after measuring 50 cycles The discharge capacity maintenance rate is 78.1%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Comparative Example 15

Except for using 3.0% by weight of 4-fluorotoluene relative to the non-aqueous electrolyte, the same operation was performed as in Comparative Example 11 to prepare a non-aqueous electrolyte to make a coin battery, and when the battery characteristics were measured after 50 cycles, the discharge capacity was maintained. The rate is 80.6%. Table 2 shows the production conditions and battery characteristics of the coin cell.

Table 2 positive electrode negative electrode compound Addition wt% Electrolyte composition (capacity ratio) Initial discharge capacity (relative value) 50 cycles discharge capacity maintenance rate% Example 11 _LiCoO2 artificial graphite tert-amylbenzene 2.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.03 92.8 Example 12 _LiCoO2 artificial graphite tert-amylbenzene 5.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.02 91.5 Example 13 _LiCoO2 artificial graphite tert-amylbenzene 0.5 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.01 90.3 Comparative Example 11 _LiCoO2 artificial graphite none 0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.00 82.6 Example 14 _LiCoO2 artificial graphite 1-methyl-4-tert-amylbenzene 2.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.02 92.1 Example 15 _LiCoO2 artificial graphite (1,1-Diethylpropyl)benzene 2.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.02 91.9 Example 16 _LiCoO2 natural graphite tert-amylbenzene 2.0 1M LiPF ₆ EC/PC/DEC/DMC＝30/5/30/35 1.02 92.8 Example 17 LiNi _0.8 Co _0.2 O ₂ artificial graphite tert-amylbenzene 2.0 1M LiPF ₆ EC/PC/MEC/DMC＝30/5/50/15 1.15 91.1 Example 18 LiMn ₂ O ₄ artificial graphite tert-amylbenzene 2.0 1M LiBF ₄ EC/PC/DEC/DMC＝30/5/30/35 0.99 92.6 Example 19 _LiCoO2 artificial graphite 4-fluoro-tert-amylbenzene 3.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 1.02 92.7 Comparative Example 12 _LiCoO2 artificial graphite Toluene 3.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 0.98 81.3 Comparative Example 13 LiGoO ₂ artificial graphite n-Butylbenzene 3.0 1M LiPF ₆ EC/PC/DEC＝3O/5/65 0.97 79.7 Comparative Example 14 _LiCoO2 artificial graphite Di-n-butylphthalate 3.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 0.97 78.1 Comparative Example 15 _LiCoO2 artificial graphite 4-fluorotoluene 3.0 1M LiPF ₆ EC/PC/DEC＝30/5/65 0.98 80.6

Industrial Applicability

According to the present invention, it is possible to provide a lithium secondary battery having excellent battery characteristics such as battery safety such as overcharge prevention, cycle characteristics, electric capacity, and retention characteristics.

Claims (15)

1. An electrolytic solution, which is a non-aqueous electrolytic solution for a lithium secondary battery in which electrolyte is dissolved in a non-aqueous solvent, is characterized in that, in this non-aqueous electrolytic solution, also contains 0.1% by weight to 10% by weight of tertiary Alkylbenzene compounds and 0.1% to 1.5% by weight of biphenyl compounds. 2. The electrolytic solution according to claim 1, wherein the tertiary alkylbenzene compound is a compound represented by (R ¹ )(R ² )(R ³ )C-φ ¹ , wherein, R ¹ , R ² , and ^R3 each independently represent an alkyl group having 1 to 4 carbon atoms, and ^φ1 represents a benzene ring which may have 1 to 5 substituents on the ring. 3. The electrolytic solution according to claim 2, wherein the tertiary alkylbenzene compound is a compound without a substituent on its benzene ring. 4. according to the described electrolytic solution of claim 2, wherein tert-alkylbenzene compound is tert-butylbenzene. 5. according to the described electrolytic solution of claim 2, wherein tert-alkylbenzene compound is tert-amylbenzene. 6. The electrolytic solution according to claim 2, wherein the tertiary alkylbenzene compound is a compound having 1 to 5 hydrocarbon groups and/or halogen atoms as substituents on the benzene ring. 7. The electrolytic solution according to claim 1, wherein the biphenyl compound is a compound represented by φ ² -φ ³ , and φ ² and φ ³ represent independently of each other and can also have 1 to 5 substituents on the ring the benzene ring. 8. The electrolyte according to claim 7, wherein the biphenyl compound is selected from the group consisting of biphenyl, o-terphenyl, m-terphenyl, p-terphenyl, 4-methylbiphenyl, 4-ethylbiphenyl Benzene, and compounds in 4-tert-butylbiphenyl. 9. The electrolytic solution according to claim 1, wherein the biphenyl compound is a compound having an oxidation potential of 4.5V or less. 10. according to the described electrolytic solution of claim 1, wherein non-aqueous solvent contains and is selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyrolactone, dimethyl carbonate, carbonic acid Methyl ethyl ester, diethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, One or more of 1,2-dibutoxyethane, acetonitrile, methyl propionate, methyl trimethyl acetate, octyl trimethyl acetate, and dimethylformamide. 11. An electrolytic solution, which is a non-aqueous electrolytic solution for a lithium secondary battery in which an electrolyte is dissolved in a non-aqueous solvent, characterized in that, the non-aqueous electrolytic solution also contains 0.1% by weight to 20% by weight of tertiary Alkylbenzene compound, and the number of carbon atoms of the tertiary alkyl group is in the range of 5-13. 12. The electrolytic solution according to claim 11, wherein the tert-alkylbenzene compound is tert-amylbenzene. 13. according to the described electrolytic solution of claim 11, wherein nonaqueous solvent contains and is selected from ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, gamma-butyrolactone, dimethyl carbonate, carbonic acid Methyl ethyl ester, diethyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, One or more of 1,2-dibutoxyethane, acetonitrile, methyl propionate, methyl trimethyl acetate, octyl trimethyl acetate, and dimethylformamide. 14. A lithium secondary battery, which is made of a positive pole, a negative pole, and a non-aqueous electrolyte, said positive pole is made of a composite oxide containing cobalt, nickel or manganese and lithium, said negative pole is made of lithium metal, Lithium alloy, or the material that can absorb and release lithium, said non-aqueous electrolytic solution is the non-aqueous electrolytic solution described in claim 1. 15. A lithium secondary battery, which is made of a positive pole, a negative pole, and a non-aqueous electrolyte, said positive pole is made of a composite oxide containing cobalt, nickel or manganese and lithium, said negative pole is made of lithium metal, Lithium alloy, or the material that can absorb and release lithium, said non-aqueous electrolytic solution is the non-aqueous electrolytic solution described in claim 11.